PEOHNIGAL INFORMATION OUT BUILDING MATERIALS

FOR T TSE IN THE DESIGN OF LOW- GOST HOUSING

TIBM - 57

* * * * * *

THE NATIONAL BUREAU OF STANDARDS

UNITED STATES DEPARTMENT OF GOMKERGE

WASHINGTON, D. G.

December -5, 1937

FATHERING PROPERTIES OF BUILDING BRISK

Freezing and thawing of saturated or partially saturated brick is the

commonest cause of disintegration, dependent for its severity on the particular section of the country in which it occurs. Although other factors have

an effect on the disintegration of brick, their consideration does not fall

within the scope of this outline, which is based on tests conducted by J. W.

Me Burney

.

For brick made from a specific clay or shale, molded by the same process

into units of the same size and shape, there are a number of measureable properties, variation in which parallels variation in degree of burning ana degree of resistance to weathering. Strength, porosity, density and color are among the properties, change in which is associated with, and dependent upon

the degree of burning.

Limits of strength, porosity, color, etc., are, in general, unsuitable

for specification control of weatherability , because of the differences in raw materials and methods of forming. For example, consider a clay that produced a dark red color when well-burned. A brick of salmon pink color made

of such a clay would probably indicate an under-burned brick. Another clay,

of differing chemical composition, may produce salmon colors in well-burned

brick.

The ratio of easily filled pore space to total pore space is related to

the resistance to disintegration by freezing and t iawing. An example of such

a ratio is Schurecht’s ratio designated as 048/35, which is the ratio of absorption by 48-hour cold-water immersion to absorption by 5-hour boiling, A

modification of this ratio consists of the absorption by 24-hour cold-water

immersion divided by absorption after 5-hour boiling, expressed as C24/ 35

.

The current (1936) Tentative Specifications for Building Brick (made from

clay or shale) of the American Society for Testing Materials, use the G24/ 35

ratio, together with upper limits on water absorption and lower limits on compressive strength for the purpose of grading brick according to weatherability.

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METHODS USED

Comparable samples of selected bricks were subjected to a number of

different methods of freezing and thawing. Among the comparisons were the

effect of freezing in contact with water, compared with freezing in air; and

the effect of different degrees of saturation of bricks at the time of freezing on speed and severity of disintegration.

Similar comparable samples were exposed to the action of weather by

"planting1

' in a brick "cemetery", according to the practice followed by the

Building Research Station in Watford, England. This method of exposure consists in standing bricks on end, half buried in soil. Panels of masonry also

have been built and exposed, using different typos of brick.

The ability of brick to withstand 51 cycles of freezing and thawing can

be measured by the combination of the following factors: not less than

2500 lb/in^ compressive strength with an absorption ratio of not more than

0.80, or a compressive strength of not less than 6000 lb/in with an absorption ratio of not more than 0.85.

It was found (l) that the probability of particular bricks fa

pass 51 cycles of freezing and thawing increases with increase in

ratio, and (2) if bricks ^exceeding 20 percent absorption by 5-hour

and less than 2500 Vo/ivr in compressive strength are eliminated,

C48/B5 provides an excellent criterion for rating the residue.

iling to

048/35

boiling

the ratio

Table 1 is a summary of results of exposure tests of 29 types of bricks.

The grading of degree of disintegration used in the column "number of specimens" is as follows:

(a) No visible effect of weathering.

(b) An amount of dusting, chipping or spalling such that not more than

one percent of the original weight of the brick is lost. In the inspection

of masonry, such slight disintegration is usually recognized by noting that

the brick in question is clean and bright compared with more resistant brick.

(c) Such a degree of spalling or structural cracking that the brick

would be objectionable in masonry either on account of its appearance or on

account of structural weakness. In general, a three percent loss in weight

is taken as separating this grade from the next.

(d) The brick is unusable. The loss in weight exceeds three percent.

Breaking of the brick into two or more pieces rates "d".

If the rule of rejecting all sampl is containing individual bricks with

C24/B5 ratios above 0.80 and with water absorption by 5-hour bpiling above

20 percent and with flat compressive strength below 2500 lb/in*' be applied,

all samples remaining except No. 28 rate "a". No 28 is a de-aired brick

concerning which there is evidence that the "true" 024/35 ratio cannot be

measured by the methods now employed.

2
Eighteen of the 29 types of bricks described in Table. 1 wore used in

the construction of a series of small panels. The following conclusions are tentatively presented: (a) partial protection of panels (capping) reduces

the degree of disintegration in comparison with unprotected pan Is; (b) less

disintegration results from exposing a brick in the face of a panel than

results from exposing a brick in the ’’cemetery 1 ' test for an equal interval

of time. If the "cemetery” exposure test is reclassified into .twotgrades

"no disintegration" and "slight to complete disintegration" there is excellent

correlation between the results of the panel exposure test and :che. "cemetery"

test.

It is recommended that when brick made in a certain neighborhood .are to

be used locally, the behavior of comparable brick in buildings it Least thirty

years old should be noted. Special attention should be given to the condition

of foundation courses and parapets.
TA3LE " T

data on bricks used in cemetery exposure .tests ARRANGED IN DESCENDING ORDER OF C24/B5 RATIOS.

CONSTRUCTION COMPLETED NOVEMBER I, 1930

INSPECTION MADE MAY 22, 1937

NO. DESCR: IPT ION * and LOCAL 1 TY C24/B5 RATIOS

AVG. MAX. MIN.

AVERAGE

COMPRESS 1 VE STRENGTH

AVERAGE

wat_r AB- SORPT 1 ON

,

24—HR COLD

NUMB ER OF SPECIMENS

DEGREE OF DISINTEGRATION2 total

lb/in2 PERCENT A B C D

1 SM ,C SALMON, HUDSON VALLEY .900 .960 .850 2890 20.4 8 14 3 0 25

2 SC ,C COMMON, WISCONSIN .898 .920 .850 2180 31.1 5 16 0 4 25

3 DP ,S COMMON, TEXAS .887 .900 .875 7405 12.7 20 5 0 0 25

4 SC ,C SALMON, BALTIMORE. MD. ^ .876 .895 .845 6815 1 1.8 0 8 7 5 20

5 SC ,S DE-AIRED, CENTRAL PENN.4

.865 .900 .835' 6 100 9.6 24 1 0 0 25

6 SM , C COMMON, DETROIT, MICH. .859 .895 .820 3640 20.2 19 4 2 0 25

7 DP ,C SALMON , D. C. 5 .855 .875 .840 3000 15.9 20 0 0 0 20

8 SC ,c LIGHT HARD, W. VA. 6 .852 .885 .820 6010 1 1 .6 257 0 0 0 25

9 EC ,C SALMON, EASTERN MD. .844 .880 .815 2825 14.

7

2 4 1 13 20

10 SM ,C LIGHT HARD, NEW ENG. .842 .900 .795 4450 15,5 15 10 0 0 25

1 1 SM ,C L 1 GHT HARD , NEW ENG. .842 .925 .735 8020 14.3 25 0 0 0 25

12 SC ,S SALMON, WESTERN MD. .329 .855 .800 1620 15.4 0 1 2 17 20

13 SM ,C HARD, HUDSON VALLEY .828 .920 .755 3725 17.4 24 1 0 0 25

14 SC ,0 SALMON, BALTIMORE, MD.* .820 .905 .630 7095 9.9 13 6 4 1 24

15 DP ,C COMMON , TEXAS .807 .9 10 .720 3550 26.8 21 4 0 0 25

16 DP ,C COMMON, D. C. 5 .30 1 .855 .745 3990 12.0 24 1 0 0 25

17 SM ,C SALMON, BALTIMORE, MD. .751 .810 .670 1830 17.3 9 1 1 9 20

18 SM,C COMMON, CENTRAL PENN. .729 .765 .645 5370 12.6 25 0 0 0 25

19 EC,C COMMON, CHICAGO, ILL. .728 .870 .555 2500 1 1 .6 17 5 3 0 25

20 SC ,C HARD, D. C. .707 .775 .515 3990 8.7 25 0 0 0 25

2 1 SAND-LIME, PHILA., PENN. .703 .735 .675 3495 13.3 25 0 0 0 25

22 EC ,C STRAIGHT HARD, PHILA., PA. .698 .740 .665 6070 11.5 25 0 0 0 25

23 SM,C SALMON, S.E. PENN. 8 .675 .710 .630 1285 16.2 25 0 0 0 25

24 SO ,S FACE, ST. PAUL, MINN. 9 .644 .830 .405 5220 10.5 20 0 0 0 20

25 SM,C HARD , NEW ENG. .639 CD O .070 13020 5.8 25 0 0 0 25

26 SM ,C HARD, NEW ENG. .614 .755 .535 1 1675 4.4 25 0 0 0 25

27 SC ,s HARD, W. VA. C .548 .625 .400 1 3410 2.4 25 0 0 0 25

28 SC,S DE-AIRED, IOWA4 .509 .965 . 155 12460 3.2 21 3 0 1 25

29 SC ,FC FACE, WESTERN PENN. .338 .370 .250 15400 0.8 25 0 0 0 25 10

*SM - SOFT MUD DP - DRY PRESS SC - SIOC CUT

EC - END CUT C - CLAY S - SKALE FC - FIRE CLAY

2 (a) NONE, (3) SLIGHT, (c) PARTIAL, (d) COMPLETE.

QoS. 4 AND 1 4 CORRESPOND EXCEPT FOR DEGREE OF

FIRING.

4 lT IS QUESTIONABLE WHETHER C24/B5 RATIOS FOR DEA 1 RED BRICKS OF THIS DEGREE OF BURNING ARE CORRECT.

5 N0S. 7 AND 16 CORRESPOND EXCEPT FOR DEGREE OF FIRING. A DIFFERENT TYPE OF EXPOSURE CAUSED A CORRESPONDING SAMPLE TO RATE "D".

°NOS. B AND 27 CORRESPOND EXOEPT FOR DEGREE

OF FIRING.

Questionable whether rating should be "A m or "3". there is a slight chipping -on EDGES OF ALL SPECIMENS.

8 N0TE THE LOW COMPRESSIVE STRENGTH.

9N0T TYPICAL SHALE. A MIXTURE OF SPECIALLY

TREATED FACE BRICK,

l0 CRAZING ON EXPOSED ENDS OF A NUMBER OF SPECIMENS. - 4 -